The present invention provides a method of chemically treating forage to improve the nutritive value of the forage.
Poor quality forages are characterized by their high fibre and low crude protein contents. This not only includes the various types of hay but also cereal straws which represent a substantial supply of potentially digestible nutrients for ruminant animals. It is generally accepted that the cell walls of plants are a complex structure of fibrillar elements embedded in an `amorphous` matrix and that the whole structure is held together by chemical bonds between many different types of polymers. The digestion of these polymers by rumen microbes will depend not only on the type of polymer present but also on the association between them. The types of microbes found in the rumen can be classified into three major groups: bacteria, protozoa and fungi.
Energy from plant carbohydrates is used by the microbes for growth, the by-products of this process are fatty acids (acetic, propionic, butyric and others), which are absorbed from the rumen into the animal's blood stream. Acetic acid and butyric acid must be used directly by the animal to produce its own energy for maintenance and growth. Propionic acid can be used to build storage polysaccharides which can be used by the animal later in life. Propionic acid is also utilized more efficiently than the other acids and this has led to concepts of rumen manipulation to improve efficiency of feed utilization by increasing the proportion of propionic acid. The microbes themselves are a rich source of minerals, vitamins, energy and protein. As they pass into the acidic environment of the true stomach (abomasum) they rupture and release nutrients which are quickly utilized by the animal. Energy is no doubt important, but for the microbes to capture it they also require nitrogen. Nitrogen enters the rumen in different forms and is degraded to various degrees by microbial enzymes into peptides, amino acids, and ultimately ammonia. Ammonia is used to build microbial protein and this process requires energy. The synchronization of energy and nitrogen availability cannot be overstressed. If energy is in short supply the ammonia concentration in the rumen rises in excess of requirements. Much of this excess ammonia passes across the rumen wall into the blood stream and is transported to the liver where it is converted to urea, a variable proportion of which is recycled, to the rumen via the saliva. Alternatively, if nitrogen is limiting, microbial growth and reproduction will be severely curtailed and result in a slow and inefficient digestion. Although supplementation with protein or non-protein nitrogen can increase animal performance, an increase in the supply of readily digestible cell walls would also be an extra benefit.
Methods of treating straw with alkali were known by the beginning of the 20th century. In 1922, Ernest Beckman developed a "wet" process for treating forage with a low concentration of sodium hydroxide. R.K. Wilson and W.J. Pidgen (Can. . Anim. Sci. 44: 122-123, 1964) developed a dry process where concentrated NaOH was sprayed onto the forage which was then neutralized with organic acid. Other methods of chemical treatment have been pursued, including:
a) potassium hydroxide (R.R. Spencer et al, 1984, Agron. J. 76: 819-824);
b) selected organic acid and base (U.S. Pat. No. 4,082,859);
c) organic waste ash (E.A. Adebowale, 1985, Anim. Feed Sci. Tech. 13: 237-248);
d) ozone (G. Shefet and D. Ben-Ghedalia, 1982, Eur. J. Appl. Microbio. Biotechnol. 15: 47-51);
e) ammonia (R.N. Gates et al, 1987, J. Anim. Sci. 64: 1821-1834; M.J. Lawlor and J. O'Shea, 1979, Anim. Feed Sci. Tech. 4: 169-175; P.J. Van Soest et al, 1984, Anim. Feed Sci. Tech. 10: 155-164);
f) sulphur dioxide (G.McL. Dryden and R.A. Leng, 1986, Anim. Feed Sci. Tech. 14: 41-54);
g) alkaline hydrogen peroxide (M.J. Gould and S.N. Freer, 1984, Biotech. Bioeng. 26: 628-631; S.M. Lewis et al, 1987, Anim. Feed Sci. Tech. 17: 179-199);
h) primary amines (F. Laurent et al, 1985, Anim. Feed. Sci. Tech. 13: 131-140);
i) acified dioxane (U.S. Pat. No. 3,937,849);
j) urea and urea phosphate (U.S. Pat. No. 3,937,846);
k) diethanolamine triacetic acid triamides (U.S. Pat. No. 4,800,213); and
1) .alpha.-haloacetamides (U.S. Pat. No. 3,564,099). All the above methods have been shown to improve the feeding value of poor quality forages but each has its limitations. For example, ammonia, ozone and sulphur dioxide are difficult to handle. The alkali NaOH and alkaline hydrogen peroxide greatly improve the availability of cell wall carbohydrates. If the ruminant is to make use of this extra carbohydrate it follows that extra nitrogen must be supplied in the diet. In this regard, compounds which improve the availability of cell wall carbohydrates in addition to providing nitrogen are disclosed in the present invention.
Specifically, hydrogen peroxide in combination with ethanolamine or another non-toxic amine with or without the addition of sodium hydroxide was found to be preferred. This combination of compounds provides an unexpected improvement over the prior art combinations in that when used according to the invention, it gives an in sacco improvement in the fiber digestion of certain forages and thus improves their nutritive value.